Is finding a pukka neurosignature for pain on the top of our discovery list?

Earlier this month, Nature Reviews Neurology published a Consensus Statement from a presidential taskforce of the International Association for the Study of Pain (IASP), on the use of brain imaging tests for chronic pain. The statement answers the question of whether chronic pain can be identified ‘objectively’. Whether or not brain imaging can provide a ‘neurosignature for chronic pain’ (i.e. provide diagnostic differentiation) has been hotly debated over recent years; the medicolegal and ethical implications of this are not trivial. Overall, the authors of this Consensus Statement emphasise that, while brain imaging has the potential to increase our understanding of the neural mechanisms underlying pain, predict individual outcomes from pain management interventions, and find targets for therapeutic agents, its use in the context of diagnosis is still in a discovery phase. While we think that this is a realistic and responsible conclusion for the present, a few concerns about the statement remain.

Our first concern is that although the authors themselves state that brain imaging should be used as an adjunct, not a replacement, for pain reports, they go on to suggest that neuroimaging could be “particularly valuable for nonverbal populations (…disabled, very young or have dementia…), cases in which the evidence from verbal reports and behavior is conflicting…” We find this a worrying take-home message. Once upon a time we used back x-rays to tell us whether someone really had back pain. If we aren’t careful we may find ourselves coming full circle, using a brain image of proof of someone’s pain report. Just as a back x-ray did not tell the full story, neither does a brain image, in our opinion.

Why might brain imaging fail to tell us the whole story? Well there is one big issue that was not raised in the statement, and we were surprised by its absence. The issue is ‘the hard problem’ [1] of how and why physical processes might give rise to experience. Surely this argument needs to take place before any questions of technology or methods of analysis are asked.

We argue that brain imaging can provide us with, at best, objective correlates of some of the subjective experience of pain. But, can you find features such as time, knowledge, meaning, and social context in the physical properties of the brain – with objective measures such as brain regional blood flow, or varying connectivity of neurons? Even if you take the point of view that pain subjectivity is partly physical (some reports of abolition of pain with brain injury might support this), and partly a social construct involving experience, et cetera, the idea that we might discover a pukka brain biomarker of pain might need a revolution in a few other fields first.

We acknowledge that such a big philosophical question has the field divided. Some people would argue that pain – a subjective experience – exists outside the brain – that the brain is necessary, but not sufficient for pain (Derbyshire [2]). Others believe that the hard problem will resolve if we find out how the brain works. They argue that more fine-grained analysis tools such as MVPA [3], big data sets, or technological advancement will enable us to identify the neurological mechanisms that generate pain. This concept, of objective correlates of a subjective experience, is crucially important to this debate and we believe it deserved at least a paragraph of airplay.

Another interesting omission for us in this discussion is that of suffering. We don’t try to image suffering – why is that? Pain and suffering are not the same, but is it not the suffering that we are trying to ease? If a person presents with pain and no suffering we perhaps don’t feel the same urge as a clinician or caring health professional to ‘do something’; one of the imperatives that drives this discussion is our desire as researchers and clinicians to better understand pain and help people who suffer from pain. Would an objective measure be able to account for this component of the pain story?

Overall we think that the risks associated with using brain imaging as a test for chronic pain are considerable, and not worth taking with what we have available to us at this stage. We wish for a broader debate about the appropriateness and validity of chasing a diagnostic measure for chronic pain. We must take responsibility as scientists. The authors state, as part justification for this Consensus Statement, that “Patients seek objective testing to demonstrate the reality of an invisible condition that is sometimes subject to doubt…”. Indeed chronic pain may be yet invisible, but with a few exceptions it is not inaudible. That is, a patient’s report of pain should not be subject to doubt. And in using brain imaging, as it stands, as a test for pain we run the risk of buying into this doubt. We believe we are better off empowering patients with education and explanations of the complexities of pain and its subjectivity than buying into the temptation to demonstrate that someone is in pain.

About Carolyn Berryman

Carolyn finished her PhD with BiM in 2015 exploring chronic pain, somatic hyper vigilance and cognitive function and is pursuing her research and teaching interests in chronic pain and cognitive function with clinical application.

Carolyn has masters degrees in physiotherapy and medical science (pain management). Before winning an Australian Postgraduate Award to return to study she taught pain sciences to under and post graduate physiotherapy students at UniSA with the Noisters and ran her own clinic for a couple of decades. Way back in 1995 she was co-convenor of the inaugural Moving in on Pain conference in Adelaide. Now she uses that experience to inspire and mentor the next generation of interest in pain sciences at Uni SA.

About Flavia Di Pietro

Flavia Di Pietro completed her PhD with the Body in Mind Sydney group early in 2014. Her project used functional MRI to investigate the brain’s patterns of activity in people with complex regional pain syndrome (CRPS) of the upper limb. She now works as a post-doctoral researcher at the University of Sydney with Associate Professor Luke Henderson. They are researching the electrical and chemical function of the brain in people with chronic orofacial pain.

Are you young with CRPS? We need your help!

Young people with CRPS and parents/caregivers are needed for research being conducted at Bath University

The study involves asking young people (14-25 years) with CRPS and parents of young people with CRPS to complete a 20-25 online survey which asks them to think about their future. Study recruitment is being conducted separately for both young people and parents. Please email crpsstories@bath.ac.uk if you would like to take part. Participants will be paid for their time.

PainAdelaide 2019

For you interstaters / internationallers – it is the day after Womad so combine a trip to the Festival City with one of the world’s truly great music festivals. Put it in your diary and we will let you know as soon as registration is up and running.

It’s impossible to slip your disc!

Lorimer Moseley answering the question “What is the thing that annoys you most when we talk about back pain?”

Online survey on bodily changes, sensations, and mood in people with chronic pain

How do CRPS and other chronic pain conditions affect bodily functions, sensations, and mood? Help CRPS researcher Janet Bultitude find out by responding to her survey.

The survey is aimed at people with CRPS, people with chronic pain conditions other than CRPS, and people without any chronic pain condition. The survey takes approximately 20 minutes and the responses are anonymous.

Prof Paul Hodges on pain and altered movement

Am I safe to move?

Listen to Lorimer Moseley talk to Karim Khan on new understanding of pain and focusing on the patient.

Understanding Pain

Regular physical activity is important for our health and well-being. Recent evidence suggests that independent of being physically active, limiting the duration of sedentary behavior, such as sitting or lying down, is important to reduce the risk for cardiovascular disease, diabetes, cancer and all-cause mortality (Biswas et al. 2015). Advances in wearable sensors provide a […]

We don’t normally have to think about our breathing and that’s because breathing is handled by a subconscious part of the brain called the medulla. The medulla automatically controls our breathing as well as our heart rate and blood pressure (Del Negro et al. 2018). It sends neural signals to the breathing muscles to activate them […]

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All blog posts should be attributed to their author, not to BodyInMind. That is, BodyInMind wants authors to say what they really think, not what they think BodyInMind thinks they should think. Think about that!

We aim to facilitate and disseminate good clinical science research. We love comments that engage with the research and are constructive and respectful. We do not prescribe treatments. Promotion of your particular therapy in the comments section is not appropriate here either - that is not the point of BiM. Finally, all the comments that are made reflect the views of the person who made them and are not endorsed by BiM or members of the BiM research group.